I have a 8.5kw electric shower which has stopped working, looking in the
fuse box the Wylex (push in type, not mcb) carrier and fuse are burnt!

The shower was fitted many years ago by Southern Electric, so I can only
assume the cable is correct. I replaced the actual shower unit with a new
one, pratically identical one from Wickes/Triton.

Should I be concerned about this?. I can easily replace the fuse and
hopefully catridge, but it has scortched some of the bit the fuse plugs
into - can this be replaced.

any ideas would be appreciated

By my calculations, 8.5KW @ 240v is 35.4A

Maybe somthing to do with it?

Sparks...